The maverick singer is spreading her wings. She's writing a feminist fairytale for the National Theatre, she tells James McNair. Photos by Teri Pengilley.

"There's nothing wrong with Disney," says Tori Amos, "but my benchmarks are more West Side Story meets Jesus Christ Superstar. I'm trying to write a musical that will be relevant to a 16-year-old today, a rite of passage for a young girl into womanhood.

"The National Theatre [with whom she's in talks] has been more open-minded than anyone I could have worked with on Broadway, but everything has to be approved by committee, and I have to tell you that not everyone is aboard my Bosendorfer rocket-ship. They can pull out and this musical may never be staged, but I don't want to be writing for a fuddy-duddy audience."

We've ostensibly met to discuss Amos's upcoming DVD release Live at Montreux 1991/1992, but for now we're talking about the stage adaptation by her and the playwright Samuel Adamson of George MacDonald's 19th-century fairy tale The Light Princess.

It figures that Amos, 45, once dubbed "Queen of the Fairies", should be attracted by a story about a princess whose lack of gravity causes her to float above the world. But as the North Carolina-born singer and pianist points out, MacDonald's fantastical allegory has substance and a malleable, enduring resonance, the princess's "lightness" being a vehicle for Amos to explore modern-day illnesses such as anorexia, and other elements of MacDonald's work lending themselves to environmental themes.

This being Amos, we can expect the work (which she hopes to complete by 2010) to be packed with feminist ideas. "The thing about the original story I wasn't crazy about is that the princess's disability gets blamed on an old hag," she says. "We're not going to deal in spells cast by old ladies; we're dealing with problems caused by power and greed, many of which start with men."

Amos says some of the music in the piece is Wagnerian in approach, while one song, "Delectable Guy Pain", was partly inspired by the Shirley Bassey hit "Big Spender". There's an aria for the princess that Amos likens to a darker take on "Memory" from Cats. "Whatever you think of Andrew Lloyd Webber, he knows what he's doing with a melodic arc," she adds.

Like this year's Comic Book Tattoo -- a 480-page interpretation of Amos's songs by various graphic novelists -- The Light Princess demonstrates the singer's desire to diversify. With albums as conceptually daring as 2005's apiary/gnostic gospels-informed The Beekeeper behind her, one can see why Amos would need a fresh challenge, but her move to cover more bases also seems driven by her recent split from Epic Records and the uncertainties that has brought in its wake.

Amos's contract with Epic was drawn up in 1999. Back then, the music industry was in robust health, but by the time she had delivered her fourth album to Epic, a general decline in sales throughout the industry had made the terms of her deal almost impossible to meet.

In April this year, the singer managed to extricate herself. "I have my sovereignty now," she says, "so I'm having all these dates with record companies and distributors. Some are new faces and some are people I might have been married to many years ago. Do I go with my ex-husband's brother or do I go back with my first husband? It's tricky, but it's sexy to be holding all the cards."

Lest Amos's metaphor-speak confuses, she is married to the British sound engineer Mark Hawley. The couple met on Amos's Under the Pink tour in 1994 and currently live between homes in Cornwall and Florida, with their daughter Natashya. Having split with Epic, Amos is financing recording sessions for her as-yet-untitled 10th studio album herself (again there's a concept; each song will be tied to its own short film), but with 12 million album sales and a vast, famously loyal fan base behind her, the singer surely needn't worry about this winter's fuel bills?

"I don't have endless amounts of cash to plough into things," she says, "but we've been fairly careful. We didn't buy any Ferraris – my husband has to watch Top Gear for his metal pornography. There's actually a part of me that worries I might be spending Tash's university money, but she's fine with that. She's like, 'It's OK, Mummy, go rock; I might not want to go to college anyway.'"
Unlike most eight-year-olds, Natashya Lorien Hawley has already been around the world four times. She has an iPhone. "She's learning piano and a bit of guitar," says her mother, "but she wants to be a film director and her main thing now is taking pictures. When I look at what she's doing on Photoshop it's clear to me that her eye sees something different because of the rich experiences she's had."
The Live at Montreux 1991/1992 DVD is noteworthy because its pair of year-apart performances bookend the success of Amos's debut Little Earthquakes, which reached No 14 in the UK album charts on its release in January 1992. Prior to that Amos often topped the bill at entry-level UK venues such as the Mean Fiddler in Harlesden, north London. "I'd take the Tube and walk the rest," she says. "I didn't know where the hell I was."

It was, Amos admits, "a bit of a headrush" when the impact of Little Earthquakes led to her face all over MTV and thousands of billboards. "But there was a rosier side to non-success," she says. "There's romance involved when people are discovering you. But then they begin to see your faults. Now, 16 years on, things feel different again, of course. People want to trade in their Ford for a new model -- you can't be a '68 Jag forever."

Still, Amos shows no signs of slowing down. She says that her brother Michael's death in a car crash in 2004, aged 50, "burst the bubble of immortality" for her. "Life is fleeting," she adds, "and in the light of that you have to seize the day."

A stint filming some of the silent movies that will accompany Amos's new album is scheduled for two days after our interview. She has also contributed to Carrie Borzillo-Vrenna's new book Cherry Bomb, partly "a guide to becoming a better flirt", and has recorded a duet with David Byrne for his forthcoming record Here Lies Love.

If all goes well with The Light Princess, Amos plans a comic-book version. She says it's the promotional side of things rather than the creative that can be wearing: "Sometimes you can have great conversations, but unfortunately there are also journalists who want to get you divorced."

We breeze through different topics. Amos tells me she doesn't ride on her husband's motorcycle for fear of damaging her fingers, but that she does take the jet-ski for a spin when in Florida. She says Tash demonstrated her Democratic leanings by scrawling "Vote Obama!" on FedEx boxes dispatched from the Amos household, and that her father Edison, a former Baptist minister, has started learning the piano aged 80 and is progressing well despite his arthritic digits.

"My parents are actually running across America like teenagers right now," Amos adds. "My dad's got this John Deere tractor from the farm he grew up on, and my mom sits up back – it's like a scene from Oklahoma!. When they visit me on tour we want to get them a nice room, but they're from the Depression era and they always insist on some budget motel.

"They're still madly in love, too. They've both come close to death and now they know that they are staring the physical end right in the eye. They've told me they feel like two old oak trees whose job is to be strong so that the rest of the family can come sit under them and find shelter and stability. I think that's pretty great."